New Free Tubes Day: GZ34 & other goodies. Help ID'ing the GZ34

[Custom Deluxe]

OK, so I was at my Dad's house and he said some guy that he knows gave him a box of tubes. The guy he got them from use to work for HP. Makes sense since some of the 12AT7's that were in the box were have HP silk screens and are made in Japan. These came in HP-labeled cardboard tubes.

A few of the tubes are US-made 6201's (industrial grade & low noise 12AT7's). There was also some US-made 12AU7's and other big tubes like 6080's and other radio tubes (4 digit types). Most are in white JAN-labeled boxes. A few are in GE boxes. I really have no use for the other tubes and will try to narrow down what they are for. More than likely radios and test equip.

Here is the prize:

While looking through the box, I also found a RCA-labeled, made in Gt. Britian 5AR4/GZ34 rect. tube.

I don't have a pict at this time, but how do I know if this is a re-labeled Mullard?

It doesn't have the "tell tale" small hole in the locating pin and the top glass has a ridge/seam in it.

I'll try to get a pict. posted. In the meantime, what codes should I look for and what type of plate structure would help we narrow the manufacture down?

Thanks,

CD

[vibrasonic]

The seam usually means its made in Japan. If you look really close it looks like an x on the top.

They are good quality 5ar4's , much better than whats being made today by far.

They will usually have a smaller bottle than the british or euro GZ34's.

[Custom Deluxe]

Really? Even with it saying made in Gt. Britian? The seem is only one way.

I also have a known to be real Amprex Buggle Boy that has a the seem in the top.

The plot thickens...

Thanks for the reply.

Originally Posted by vibrasonic

The seam usually means its made in Japan. If you look really close it looks like an x on the top.

They are good quality 5ar4's , much better than whats being made today by far.

They will usually have a smaller bottle than the british or euro GZ34's.

[bdgregory]

Post your question on Tubes Asylum. You will get multiple responses from authorities on tubes.

It doesn't seem likely that an RCA tube would be made in Japan, and be labeled made in Gr Britain, but I'm far from an authority on the matter.

[slider313]

Look for etched codes near the base; I61, I63, I65

[uriah1]

-Not sure if it is nonsense, but, someone once told me to look for pin hole in bottom
of main plastic cyclinder extrusion. Only Mullard did this.

[Wally]

Pictures???

[Custom Deluxe]

I'll get some and post them later.

[BiggerJohn]

Originally Posted by vibrasonic

The seam usually means its made in Japan. If you look really close it looks like an x on the top.

They are good quality 5ar4's , much better than whats being made today by far.

They will usually have a smaller bottle than the british or euro GZ34's.

+1.

[Custom Deluxe]

Here are some pictures of the GZ-34. See what you think.

[Wally]

I was looking for some numbers near the bottom of the glass envelope, but that tube doesn't look like a Mullard to me.

[Custom Deluxe]

Originally Posted by Wally

I was looking for some numbers near the bottom of the glass envelope, but that tube doesn't look like a Mullard to me.

Wally:

I'd have to agree. Just doesn't seem like a top notch tube, if that makes sense. I think it is a Japenese made tube.

[Wally]

It might be a fine tube. If it doesn't rattle and if it provides correct voltages, it is good to go, imho. Someone won't give you 'stupid money' for it like they would if it were a Mullard.

[Custom Deluxe]

Originally Posted by Wally

It might be a fine tube. If it doesn't rattle and if it provides correct voltages, it is good to go, imho. Someone won't give you 'stupid money' for it like they would if it were a Mullard.

Yeah, I had not intent to sell, just would like a good GZ34 for a spare for later on down the road.

Thanks again for the input...

[Wally]

IF a person had an amp on the bench that used GZ34/5AR4 rectiifer tubes, it would be interesting to install that tube and compare it against a known GZ34 and to test it for microphonics/rattling.